Today's television delivery systems are designed to deliver analog video/audio signals from the signal source to viewer televisions. With the introduction of digital technology for video/audio, the future of television delivery systems requires conversion of the delivery systems from analog to digital video/audio.
Developments in digital bandwidth compression technology will allow for much greater throughput of television program signals over existing or slightly modified transmission media. The cable television delivery systems must be redesigned to take advantage of digital technology. The cable headend is a key part of a cable television delivery system and requires redesign.
Analog cable television delivery systems operate with an analog cable converter box in the viewer home which uses a television to display video programs. The converter box is connected via cable to a cable headend site.
Typically, each analog cable headend site has multiple satellite dishes. Each analog cable headend site's satellite dishes normally receives transponded signals from one or two satellites. A satellite has multiple satellite transponders. Although uplink sites and satellite dishes can transmit and receive multiple video/audio program signals, currently, each satellite transponder normally carries only one video/audio program at any given time. Typically, a transponder is dedicated to one channel of video programming. Further, there is generally one Integrated Receiver and Decoder per transponder (or channel) at the analog cable headend to receive the signal from the transponder.
In summary, current analog technology requires the combination of one uplink site, one satellite transponder, and one cable headend satellite dish to deliver each analog video/audio program to the cable headend. The cable headend uses several analog video/audio signals from multiple dishes and multiple transponders to provide multi-channel analog signals. The cable headend then transmits these analog signals on different transmission frequencies to the cable converter boxes in the viewer homes where one channel is selected.
Each television channel for analog video/audio transmissions for television is in a 6 MHz segment of bandwidth. An industry standard of 6 MHz was set in the year 1939 and the NTSC standard is still 6 MHz per channel of analog video. As television program delivery technology moves into the digital world the 6 MHz segments have no real technical significance, except in hybrid analog-digital converters.
In addition, today's cable television delivery systems carry signals which are scrambled for security reasons. Each vendor uses scrambling techniques that are incompatible with the every other vendor. There are two primary cable industry leaders in scrambling formats, Scientific-Atlanta, Inc. (SA), 4386 Park Drive, Norcross, Ga. 30093 and General Instrument Corporation, Gerald Communications Division (GI), 2200 Byberry Road, Hatboro, Pa. 19040.
Currently, a two step scrambling/descrambling process is used in cable television program delivery systems. During the first step, program signals are scrambled prior to satellite transmission and are descrambled at the cable headend. During the second step, program signals are transmitted in scrambled format to the viewer homes where an authorized converter box descrambles the signals. Primarily, two types of scrambling techniques are used between the cable headend and converter boxes in subscriber homes, video inversion and synch suppression. Thus, the final descrambling takes place at the converter box in the viewer homes using one of these two techniques.
General Instruments is by far the industry leader and has a virtual “lock” on the market for signal scrambling from origination point to cable headend. From the cable headend to the subscriber home, General Instruments and Scientific Atlanta have the greatest market shares, but face competition from competitors such as Zenith and Pioneer. Scientific Atlanta and General Instruments are also the primary producers of set top terminals for the U.S. cable industry. Therefore, cable headends may only service one vendor's converter boxes. Generally, cable headend scrambling equipment services either Scientific Atlanta converters or General Instruments converters. No standard scrambling or security measures have been agreed upon by the industry. In some cases, manufacturers can produce descramblers that are compatible with another's system.
Although no standard method for digital coding of moving pictures and audio has been established, the television industry through the International Organization For Standardization is working on a digital coding standard.
The use of digital video/audio signals for delivering cable television programming will require changing today's cable television delivery system. In particular, the analog cable headend described above will not operate in the digital environment. Methods of encryption and decryption also need to be examined.
What is needed is a cable headend which operates in the digital environment.
What is needed is a cable headend which can operate in both the digital and analog environment.
What is needed is a cable headend which receives multiple video/audio program signals from a single satellite transponder.
What is needed is a cable headend which can combine digital video/audio program signals for transmission to viewer homes.
What is needed is a cable headend which can send both analog and digital video/audio program signals to viewer homes.
What is needed is a cable headend which can combine selected analog and selected digital video/audio signals to be transmitted to viewer homes.
What is needed is a cable headend which can select discrete digital channels from a multiple digital channel feed and recombine the channels for transmission to the viewer home.
What is needed is a cable headend that can combine various digital video/audio signals to create tiered program offerings for viewers.
What is needed is a cable headend that can handle any necessary signal encryption or decryption.
Accordingly, there is an unanswered need for digital cable headend technology. There is a need for cable headend technology that takes advantage of digital compression techniques for video/audio program signals.
The present invention is designed to address these needs.